Process of decolorizing cellulose nitrate



Patented Jan. 8, 1935 UNITED STATES,

raoosss or DECOLORIZING CELLULOSE m'raarn Marvin J. Reid, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y.,

a corporation of New York No Drawing. Application October 4,1932, y i No. 636,1 3

4 Claims.

This invention relates to the reclamation of film scrap and particularly to a process for reclaiming colored cellulose nitrate film base.

Many processes have been suggested in the past 5 for reclaiming film scrap and particularly cellulose nitrate film scrap from which the silverhalide emulsion has been removed but, until my invention, certain types of colored cellulose nitrate film base have defied reclamation, for the reason that it has been impossible to remove the coloring without destroying the cellulose nitrate. I have found that colored cellulose nitrate film scrap base may be reclaimed without ruining the cellulose nitrate if it is first bleached with a suitable bleaching bath, followed by treatment with an alcoholic solution of caustic alkali, after which the film base may be washed or leached with water or alcohol.

While the two principal steps of this process have been separately known and used, either alone or in conjunction with some additional step, I

have found that neither of these steps taken separately would, with any of the known supplementary treatments, operate to successfully re- 25 cover strongly colored cellulose nitrate film base for reuse.

Accordingly, it is among the objects of my invention to providea process for reclaiming strongly colored cellulose nitrate film base or support for reuse in the art. Other objects will appear to those skilled in the art upon a further perusal of this specification.

Many cellulose nitrate film negatives have the back (non-emulsion) side thereof strongly colored 35. or backed with a coloring or backing of some strong color or coating which will reduce or eliminate halation during the exposure of the film in the camera. These non-halation backings are frequently composed of a strongly dyed solution or mixture of cellulose acetate, protein, albumin, or

some other colloidal substance. While these socalled non-halation backings very effectively perform their purpose of eliminating halation, they are very difiicult of removal from the cellulose nitrate film base when it is sought to recover the base for reuse.

I have found that cellulose nitrate film base of this general charactermay be completely recovered and decolorized for reuse by first bleaching the scrap (from which the emulsion has been removed) in a solution of a hypochlorite of an alkali metal, followed by treatment of the support in an alcoholic caustic solution. The treatment is, of course, more effective if the sheeting is first cut into small pieces a fraction of an inch square,

Serial '1 although this is not essential. I may, for instance, bleach the foregoing cellulose nitrate base (from which the emulsion has been removed as,

for instance, by soaking it in hot water) by bleachble salts which have been precipitated upon the film support. I then immerse the so-treated nitrate film base scrap in an ethyl alcohol solution of approximately .2%' sodium hydroxide (more or less) which is prepared by adding to the alcohol a 40% solution of alkali hydroxide. This alcoholic caustic solution is maintained at about 120 F. and the treatment continued for about five minutes. The alcoholic solution may then be drained off or the film scrap removed, after which it is washed either in warm or hot water, or in two one hour leaches, with ethyl alcohol at 120 F., in

order to remove all traces of solutionfsodium hydroxide or decomposition products. A similar treatment using potassium hydroxide or other well known caustic is likewise effective and operative in my process. Other alkali metal hypochlorites may also be used in place of the calcium hypochlorite.

Cellulose nitrate film scrap so treated will be found to be quite clear and free from color or other backing materials which would contaminate the cellulose nitrate for reuse. The bleaching treatment does not allow reclaiming the cellulose nitrate even when followed by an alcohol leach, nor does the treatment with the alcoholic caustic completely reclaim this type of cellulose nitrate film base, even when followed by an alcohol leach. Accordingly, the two principal steps involved in my process are necessary to be operated in combination in order to effectively reclaim the strongly dyed or backed type of cellulose nitrate film base scrap.

What I claim, and desire to secure by Letters Patent in the United States is: i

1. The process of removing difficultly removable dyed, colloidal, non-halation backings from cellulose nitrate sheeting which comprises subjecting the sheeting to the bleaching action of an alkali metal hypochlorite solution and then treatdyed, colloidal, non-halation backings from cellulose nitrate sheeting which comprises subjecting the sheeting tothe bleaching action of an alkali metal hypochlorite solution containing about 2% available chlorine and then treating the sheeting. with about a .2% solution oi caustic alkali in alcohol.

v 3. The process of removing dimcultly removable dyed, colloidal, non-halaticn backings from cellulose nitrate sheeting which comprises subjecting the sheeting to the bleaching action 0! calcium hypochlorite solution and then treating the sheeting with an alcoholic solution of sodium hydroxide.

4. The process oi removing difllcultly removable dyed, colloidal, non-halation backings from cellulose nitrate sheeting which comprises subjecting the sheeting to the bleaching action oi. calcium hypochlorite solution containing about .2% available chlorine and then treating the sheeting with 10 about a 3% solution of sodium hydroxide in alcohol.

MARVIN J. REID. 

